US5365285A - CRT display device with a grounded rimband so as to suppress an electro-magnetic emission - Google Patents

CRT display device with a grounded rimband so as to suppress an electro-magnetic emission Download PDF

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Publication number
US5365285A
US5365285A US07/670,197 US67019791A US5365285A US 5365285 A US5365285 A US 5365285A US 67019791 A US67019791 A US 67019791A US 5365285 A US5365285 A US 5365285A
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United States
Prior art keywords
chassis
rim band
conductive
electrically connecting
envelope
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Expired - Fee Related
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US07/670,197
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English (en)
Inventor
Isao Kizuya
Kenkichi Yamashita
Kunihiko Onuma
Akira Hoshikawa
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Hitachi Ltd
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Hitachi Ltd
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Assigned to HITACHI, LTD. reassignment HITACHI, LTD. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: HOSHIKAWA, AKIRA, KIZUYA, ISAO, ONUMA, KUNIHIKO, YAMASHITA, KENKICHI
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/86—Vessels; Containers; Vacuum locks
    • H01J29/88—Vessels; Containers; Vacuum locks provided with coatings on the walls thereof; Selection of materials for the coatings

Definitions

  • the present invention relates to CRT display equipment, and in particular to a CRT display unit in which it is possible to significantly reduce electromagnetic radiation leaking from the front panel thereof in a simple and effective way.
  • the input rectangular waveform image signals contain a large amount of harmonic components. Further, the higher the basic clock frequency of image signals becomes or the larger the amplified signal amplitude becomes, the greater the electromagnetic radiation becomes.
  • an object of the present invention is to provide a CRT display unit which is capable of attaining the required values imposed by regulation on such units with respect to EMI.
  • an electromagnetic shield plate with a shadow mask in a CRT envelope which shield plate is electrically connected to a rim band and is further fastened to the chassis by means of metal fixtures, and by electrically connecting the rim band and the chassis by means of conductive members inserted in the space therebetween.
  • FIG. 1 is a side cross-sectional view of a CRT display unit according to the present invention
  • FIG. 2 is a perspective view of the same
  • FIG. 3 is a front elevational view of the same
  • FIG. 4 explains the effects of radiation noise level reduction in the embodiments of the present invention.
  • FIGS. 5, 6 and 7 show other embodiments of the present invention.
  • FIG. 1 is a side cross-sectional view of a CRT display unit 100 according to the present invention, where a grounded chassis 10 contains a video amplifier 50 for amplifying to a large amplitude various image micro signals having rectangular waveform and high frequency which are received from a computer (not shown in the figure), and a CRT device 105, both securely fastened to the chassis 10.
  • the envelope of the CRT device 105 comprises a funnel section 101 (facing toward the video amplifier) and a panel section 102, both glass-sealed at a joining section 103 shown in FIG. 1 by a dotted line.
  • a conductive film 3 for preventing high surge voltages
  • a conductive film 2 is deposited on the internal surface of the funnel section 101 for introducing a high voltage from an anode terminal 9 into the CRT device for election beam acceleration.
  • conductive films 2 and 3 normally graphite is used.
  • the conductive film 2 is electrically connected to the shadow mask 1, and the conductive films 2 and 3 are also electrically coupled through a coupling capacitance 4.
  • the circumference of panel section 102 is surrounded by a metal rim band 5, and the rim band 5 and the conductive film 3 are connected at spaced locations by conductive members 6.
  • the rim band 5 is further connected electrically to the chassis 10 through conductive elastic members 7 and clamping screws 8. Thereby, the shadow mask 1 is electrically connected to the chassis 10 by way of elements 1-2-4-3-6-5-7-8-10.
  • FIG. 2 is a perspective view of the CRT device 105, where the conductive members 6 referred to in FIG. 1 are shown, for instance, in the form of tape having a lining coated with an adhesive, which connects the conductive film 3 and the rim band 5 at a plurality of spaced positions.
  • the conductive members 6 are arranged so as to be not in direct contact with the joining section 103 which joins the funnel section 101 and the panel section 102. This is because air tightness at the joining section 103 is weaker than that at other portions of the CRT envelope, thereby necessitating preventive measures to be taken against deterioration of the hermetic insulation in the joint as a result of application of the conductive film 3 thereon or direct contact with the conductive members 6.
  • a high voltage insulation paper is first applied on the glass at the joining section 103, and then the conductive member 6 of the present invention may be installed thereon.
  • the tape should be made of copper or aluminum with a tape width of 1-3 cm, and its adhesive lining should also have a conductive property.
  • two strips of conductive tape have been applied to each of the four sides of the envelope, i.e. at the upper, bottom and left and right sides thereof.
  • the tape needless to say, may be replaced by a plate.
  • FIG. 3 is a front elevational view of the CRT display unit shown in FIG. 1, where the CRT device 105 is fastened to the chassis 10 by means of metal fixtures 30 formed together on the rim band 5.
  • the conductive elastic members 7 in FIG. 1 in fact, as shown in this embodiment, one part of each member 7 is fastened, for example, to the chassis 10 by means of fastening screws 8, and resilient leg portions thereof are pressed in contact with the rim band 5 by means of their resilient force.
  • the conductive elastic member 7 is provided in the form of a spring made of, for example, phosphor bronze or stainless steel, with a length of several cm, and having cushioning properties at both ends.
  • two conductive elastic members 7 are provided for each side at the top and bottom of the envelope, but these members also may be added to the left and right sides of the envelope as well.
  • the number of installations of the above-described conductive members 6 and conductive elastic members 7 may be determined appropriately according to the levels and frequencies of electromagnetic radiation leaking from the CRT display equipment. It is found, however, according to the results of our experiments pursuant to the present invention, that the reduction rate for electromagnetic radiation becomes greater with an increase in the number of conductive elastic members 7 that are employed.
  • the shadow mask 1 is electrically connected to the chassis 10 by way of the shadow mask 1-conductive film 2 - coupling capacitance 4 - conductive film 3-conductive member 6 - rim band 5 - conductive elastic member 7-fastening screw 8 - chassis 10, thereby forming an electromagnetic shield plate with the shadow mask.
  • the electromagnetic radiation 51 as shown diagrammatically in FIG. 1, is reduced substantially and is hardly permitted to leak out of the front panel of the video amplifier 50 due to the presence of this electromagnetic shield plate.
  • FIG. 4 illustrates how this embodiment of the present invention has satisfied the regulation values set by the VCCI and the FFC.
  • the X-axis indicates frequencies of electromagnetic radiation, while the Y-axis indicates levels of electromagnetic radiation detected at a distance of 10 m from the source of electromagnetic radiation. Shown in a solid line are the values of regulations set by the VCCI, while shown in a dashed line are those set by the FCC. As can be seen, the regulation values set by the VCCI are more stringent in comparison with those by the FCC.
  • the characteristic (A) represents the case of Japan Patent Laid-Open No.
  • the characteristic (B) represents the case of Japan Patent No. 62-267790 (1987), where a ground is provided by grounding at one point in the rim band 5 and at one point in the outer clad graphite portion, respectively.
  • the characteristic (C) represents the case of an embodiment of the present invention, where the rim band 5 and the outer graphite film 3 are connected at a plurality of positions through conductive members 6, and in addition, the rim band 5 and the chassis 10 are connected at a plurality of positions through conductive elastic bodies 7.
  • a CRT display unit according to the present invention is capable of being placed as near as 5 m from the noise source while holding the noise level the same at a 40 dB, at 200 MHz frequency.
  • the required distance between the CRT display unit and other electronic equipment susceptible to EMI from the unit can be cut in half.
  • FIG. 3 a conductive elastic body was used as a conductive member 7, however, there may be considered other modifications of the present invention as shown in FIG. 5, wherein a gasket 21 is inserted in the space between the rim band 5 and chassis 10.
  • the gasket 21 may be attached either to the rim band 5 or to the chassis 10 before the CRT device is fastened to the chassis 10 by means of metal fixtures 30, otherwise the gasket may be inserted in the space after the fastening has been completed.
  • both may be covered by a metal plate 22 as shown in FIG. 6.
  • the conductive film 3 coated on the bulb funnel section may be extended as far as the rim band through which it is grounded. In such cases, the improvement in preventing emission of electromagnetic radiation is afforded by the presence of the conductive member 7.
  • conductive members 6 may be electrically connected to the conductive film 3 and the rim band 5, and at the same time, for a conductive elastic body 20 to be fastened at one end to chassis 10, and press-contacted to the conductive coated film 3 at the other end.
  • CRT display equipment capable of attaining, with sufficient margin, the regulation values imposed such devices on regarding the emission of electromagnetic radiation.

Landscapes

  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Details Of Measuring And Other Instruments (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US07/670,197 1990-03-16 1991-03-15 CRT display device with a grounded rimband so as to suppress an electro-magnetic emission Expired - Fee Related US5365285A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2-64230 1990-03-16
JP2064230A JPH03266340A (ja) 1990-03-16 1990-03-16 Ｃｒｔデイスプレイ装置

Publications (1)

Publication Number Publication Date
US5365285A true US5365285A (en) 1994-11-15

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Family Applications (1)

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US07/670,197 Expired - Fee Related US5365285A (en) 1990-03-16 1991-03-15 CRT display device with a grounded rimband so as to suppress an electro-magnetic emission

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US (1) US5365285A (de)
JP (1) JPH03266340A (de)
CA (1) CA2038281C (de)
DE (1) DE4107766A1 (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5818171A (en) * 1996-01-16 1998-10-06 Samsung Electronics Co., Ltd. Device for removing electric field of display
US6211628B1 (en) 1997-08-02 2001-04-03 Corning Incorporated System for controlling the position of an electron beam in a cathode ray tube and method thereof
US6826453B1 (en) * 2000-03-22 2004-11-30 Storage Technology Corporation Method and system for emission suppression in detection of data cartridge labels
US20050006118A1 (en) * 2003-06-26 2005-01-13 Emc Corporation Adaptable emi/rfi shielding for a front-panel attachment to an enclosure
US20050087365A1 (en) * 2003-10-01 2005-04-28 Hee-Man Kim Electronic device having bezel structure
US20050264142A1 (en) * 2004-05-25 2005-12-01 Emc Corporation Locking mechanism for securing the bezel of an electronics enclosure to a rack structure
US7585005B1 (en) 2006-03-23 2009-09-08 Emc Corporation Locking mechanism for securing bezels

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0513981A (ja) * 1991-06-28 1993-01-22 Mitsubishi Electric Corp 陰極線管デイスプレイ装置
JPH05266829A (ja) * 1992-03-18 1993-10-15 Mitsubishi Electric Corp 陰極線管
JP2708324B2 (ja) * 1992-04-23 1998-02-04 三菱電機株式会社 陰極線管装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5025490A (en) * 1988-09-19 1991-06-18 Hitachi, Ltd. Cathode-ray tube with its display front protected from undesirable electrification
US5145434A (en) * 1991-06-26 1992-09-08 Digital Equipment Corporation Video display device and method of mounting a cathode ray tube in a cabinet of a video display device

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3271516A (en) * 1962-10-22 1966-09-06 Owens Illinois Inc Implosion resistant cathode ray tube with integral mounting elements to facilitate installation
DE1639037A1 (de) * 1967-07-04 1971-01-21 Rudolf Wittenbecher In sich geschlossener Bandrahmen fuer die implosionssichere Ummantelung des Glaskolbens einer Bildroehre
US3996491A (en) * 1974-08-26 1976-12-07 Gte Sylvania Incorporated External connective means for a cathode ray tube
US3952152A (en) * 1974-10-29 1976-04-20 Teletype Corporation CRT shield
NL7708958A (nl) * 1977-08-15 1979-02-19 Philips Nv Kathodestraalbuis.
JPS597731Y2 (ja) * 1979-06-07 1984-03-09 ソニー株式会社 陰極線管装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5025490A (en) * 1988-09-19 1991-06-18 Hitachi, Ltd. Cathode-ray tube with its display front protected from undesirable electrification
US5145434A (en) * 1991-06-26 1992-09-08 Digital Equipment Corporation Video display device and method of mounting a cathode ray tube in a cabinet of a video display device

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5818171A (en) * 1996-01-16 1998-10-06 Samsung Electronics Co., Ltd. Device for removing electric field of display
US6211628B1 (en) 1997-08-02 2001-04-03 Corning Incorporated System for controlling the position of an electron beam in a cathode ray tube and method thereof
US6826453B1 (en) * 2000-03-22 2004-11-30 Storage Technology Corporation Method and system for emission suppression in detection of data cartridge labels
US20050006118A1 (en) * 2003-06-26 2005-01-13 Emc Corporation Adaptable emi/rfi shielding for a front-panel attachment to an enclosure
US6870093B2 (en) 2003-06-26 2005-03-22 Emc Corporation Adaptable EMI/RFI shielding for a front-panel attachment to an enclosure
US20050087365A1 (en) * 2003-10-01 2005-04-28 Hee-Man Kim Electronic device having bezel structure
US7443697B2 (en) * 2003-10-01 2008-10-28 Samsung Electronics Co., Ltd. Electronic device having bezel structure
US20050264142A1 (en) * 2004-05-25 2005-12-01 Emc Corporation Locking mechanism for securing the bezel of an electronics enclosure to a rack structure
US7232193B2 (en) 2004-05-25 2007-06-19 Emc Corporation Locking mechanism for securing the bezel of an electronics enclosure to a rack structure
US7585005B1 (en) 2006-03-23 2009-09-08 Emc Corporation Locking mechanism for securing bezels

Also Published As

Publication number Publication date
JPH03266340A (ja) 1991-11-27
DE4107766A1 (de) 1991-09-19
CA2038281C (en) 1996-03-05
CA2038281A1 (en) 1991-09-17

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Owner name: HITACHI, LTD., JAPAN

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Effective date: 20061115